Circuit maker and breaker



July 20, 1948. c. POLLARD, JR

cmcurr MAKER AND BREAKER Filed July 21, 1944 SATl/RA TED I'ITH MERCURY IN VE NT'OR c. E. POLL/4RD, JR.

ATTORNEY Patented July 20, 1948 CIRCUIT MAKER AND BREAKER Charles E. Pollard, Jr., Hohokus, N. J., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application July 21, 1944, Serial No. 545,896

3 Claims. 1

This invention relates to circuit makers and breakers and especially to sealed contact devices of the type employing liquid mercury.

It is the object of the invention to provide a mercury pool contact device which will operate equally well in any given position. It has long been known that mercury contacts or mercury wetter contacts have many desirable properties and advantages but the great drawback to the use of such contacts has been the necessity for maintaining a pool of mercury which has meant that the contact device could be mounted in but a single position. It is therefore the object of the present invention to provide a contact device which is not subject to this disadvantage.

In accordance with the present invention a pool of mercury is maintained in a sponge of metallic fibers which are wettable by the mercury so that the mercury is held in this sponge regardless of the position in which it may be placed. I

A feature of the invention is a suspended pool of mercury held at a given location through the forces of surface tension.

Another feature of the invention is the use of a mercury wettable sponge for maintaining a pool of mercury at a given location regardless of the position to which the sponge may be turned at any given time.

Another feature of the invention is the use of a mercury trap, constructed and arranged to maintain a pool of mercury in space but of insufiicient force to defeat the use of mercury from said pool upwardly and along a mercury wick dipped in said pool.

Another feature of the invention is the combination consisting of the magnetically movable contacts having mercury wetted surfaces maintained wetted with mercury by a wick dipped in a pool of mercury held in space by a mercury wetted sponge.

The drawings consists of a single sheet having three figures as follows:

Fig. 1 is a cross-sectional view of a sealed contact device employing the novel features of the present invention;

Fig. 2 is one type of mercury sponge; and

Fig. 3 is an alternative type thereof.

The contact used consists of an envelope I of glass or other suitable material. In the lower end of this unit a tube 2 is sealed through the press 3. In the upper end two electrodes 4 and 5 are sealed through the upper press 6 in similar manner. The tube 2 is used as a support for the moving armature of the switch. Thus a spring I is welded to the upper end of the tube 2 and has in turn attached to it a magnetic armature 8. A mercury wick 9 is secured to the armature 8 and extends downwardly to a point near the upper end of the tube 2. Secured to the upper end of tube 2 there is a mass I0 of metallic fibers wettable by mercury and which constitute a mercury sponge so that the lower end of the-wick 9 will be submerged in a pool of mercury. This construction has the advantage that the mercury sponge ill will be saturated with mercury and willthus hold a pool of mercury at this point regardless of the position in which the device is turned. This therefore overcomes one great disadvantage of mercury contact switching devices which has heretofore required that they be always held in a particular position.

The two electrodes 4 and 5 extend into the interior of this device and have secured thereto the contact arrangements l I and I2 respectively, each having secured thereto a small cross piece of contact material l3 and I4 respectively. These contact pieces are wettable by mercury and therefore present'a constantly renewed clean contact surface of low resistance. a

One form of the mercury sponge is illustrated in Fig. 2 and this consists of a piece of fine mesh screen l5 rolled into the form shown and secured to the supporting tube l6 by any appropriate means. This screen is of a material which is wettable by mercury.

Another form of the invention is shown in Fig. 3 where a mass of fibers H such, for instance, as those known as steel wool, are used. This may be held together by a band l8 and the whole secured to the supporting tube IS in any appropriate manner.

The term "mercury wic used herein denotes an arrangement of a pair of metal wires or a metallic element having grooves between which or in which the mercury will rise above the level of the pool by capillary action and entails the use of mercury wettable surfaces.- A mercury wick forms part of the subject-matter of my Patent Number 2,259,661, granted October 21, 1941. Metallic fibres are, filaments or wires of metal such as iron, steel, brass, copper nickel or of various alloys, a good example of which is the tangled mass of such material known widely as steel wool.

What is claimed is:

1. A contact device having mercury wetted contacts, a mercury-wettable sponge, a pool of mercury trapped in said sponge and a mercury wick for feeding said contacts from said pool.

A contact device having mercury wetted con- REFERENCES crmn The following references are of record in the flle of this patent:

Number Number UNITED STATES PATENTS Name Date Pollard Oct. 21, 1941 Harrison June 30, 1942 McCabe Aug. 3, 1943 FOREIGN PATENTS Country Date France May 22, 1924 

